Combustible cartridges

ABSTRACT

Nonmetallic cartridges having a porous casing of fiberreinforced nitrocellulose are rendered oil and water resistant by first incorporating into the casing an organosilicon compound which renders the casing material essentially impervious to liquid water but which does not substantially alter the porosity of the material and then providing a continuous coating on the surface of the casing, the coating being a room temperature curing resinous organosiloxane having from 1.2 to 1.8 organic substituents per silicon atom, the major portion of the organic substituents being lower alkyl and/or phenyl radicals.

United States Patent Hartlein et al.

[ 1 June 20, 1972 COMBUSTIBLE CARTRIDGES [721 Inventors: Robert C. Hartlein; James D. Willard D. Larson, all of Midland; Carl R. 01- son, Freeland, all of Mich.

[73] Assignee: Dow Corning Corporation, Midland, Mich.

[22] Filed: Aug. 13, 1970 [21]- Appl. No.: 63,537

{52] US. Cl. ..l02/38, l02/D1G. 1, 102/43 [51] Int. Cl ..F42b 9/16 [58] Field of Search 102/38, 40, DIG. I, 42, 103,

[56] References Cited UNITED STATES PATENTS 3,293,056 12/1966 Baker ..IOZ/DIG. l

'I It 3,513,776 5/1970 Driscoll ..102/DlG.l 3,550,532 12/1970 Zimmerman ..l02/43 Primary Examiner-Samuel W. Engle Attorney-Robert F. Fleming, Jr., Laurence R. l-lobey, Harry D. Dingman, Howard W. Hermann and Norman E. Lewis ABSTRACT Nonmetallic cartridges having a porous casing of fiber-reinforced nitrocellulose are rendered oil and water resistant by first incorporating into the casing an organosilicon compound which renders the casing material essentially impervious to liquid water but which does not substantially alter the porosity of the material and then providing a continuous coating on the surface of the casing, the coating beinga room'temperature curing resinous organosiloxane having from 1.2 to 1.8 organic substituents per silicon atom, the major portion of the organic substituents being lower alkyl and/or phenyl radicals.

13 Claims, 2 Drawing Figures P'A'TE'N'TEnJunzo 1912 3.670. 649

INVENTORS. Rosemc. RTL6/N JAMES 0. Es

WIL LHRD 0. LARSON CARL 1?. 01.50:

ATTO NE) COMBUSTIBLE CARTRIDGES This invention relates to an improved combustible cartridge. In one aspect, the invention relates to a fiber-reinforced nitrocellulose cartridge casing which is resistant to penetration by oil and water.

Combustible cartridge cases composed of low-nitrogen nitrocellulose, reinforcing fibers and a resinous binder have been developed. The combustible case functions as a container for a propellant charge and is fitted with a metal projectile to provide a cartridge. Such a cartridge has the advantages of lighter weight and lesser cost because of the elimination of the conventional metal casing. When dry, the cartridge case is truly combustible leaving a little or no residue in the breech of a gun after firing. When exposed to high humidity or rain, the combustibility of the nitrocellulose case is adversely affected and, upon firing, a substantial amount of residue is left in the breech of the gun. Of course, contact with oily substances, such as hydraulic fluid, adversely affects the firing characteristics of the combustible cartridge.

By practice of the present invention wherein combustible cartridge cases are rendered impervious to oil and moisture, the firing problems associated with the nitrocellulose cases are minimized and the necessity of special handling and storage is eliminated.

Thus, it is an object of the invention to provide an improved combustible cartridge.

It is another object of the invention to provide a combustible cartridge which is insensitive to the effects of oil and water.

These and other objects of the invention will be apparent to one skilled in the art upon consideration of the following disclosure and claims.

According to the invention, there is provided, in a combustible cartridge having a porous casing composed of a fiberreinforced nitrocellulose which forms an exterior cartridge surface, the improvement consisting essentially of a. a water-repellent organosilicon compound incorporated into the casing in an amount sufficient to render the casing substantially impermeable to liquid water, the organosilicon compound being selected from the group consisting of alkali metal salts of a monoorganosiliconates in which the organic group is a lower alkyl radical of from one to three inclusive carbon atoms and silanes of the formula R,,SiX and water-soluble hydrolyzates thereof, in which R is a monovalent hydrocarbon radical of from 1 to 30 carbon atoms, X is a hydrolyzable group and n is an integer having a value of 1 to 3; and

b. a continuous coating on the exterior casing surface of a room temperature curable organosiloxane resin having an average of from 1.2 to 1.8 organic groups per silicon atom, at least 80 mol percent of the organic groups being selected from the group consisting of lower alkyl and phenyl radicals, any remaining organic groups being selected from the group consisting of alkoxy radicals of from one to four carbon atoms, acyloxy radicals of no more than eight carbon atoms and ketoxime radicals.

The drawings illustrate the above-defined improvement. In the drawings, wherein like reference nummerals denote like elements in the different figures,

FIG. 1 is a schematic cross-section of an assembled combustible cartridge and FIG. 2 is a broken cross-section of a portion of the cartridge casing. As shown in FIG. 1, the assembled combustible cartridge includes a metal projectile 10, attached either mechanically or adhesively to the upper rim portion 11 of the cylindrical combustible case which is designated generally by the numeral 12. A propellant 13, such as nitrocellulose, is contained in casing 12 and is ignited by a fast burning explosive 14, such as black powder, which is detonated by means of a primer element 15. The cartridge case 12 consists of a tubular casing 16 and a base member 17 which can be attached to the bottom portion of casing 16 by mechanical or adhesive means 18. If desired, the case 12 can be molded as one piece. The exact configuration of the above described elements forms no part of the present invention and can be varied according to design specification.

The case 12 is composed of low-nitrogen nitrocellulose, reinforcing fibers and a resinous binder. To ensure combustibility, the casing material must be porous. The porosity or void content is thought to allow flame propagation thru the case upon ignition of the main propellant charge 13 and provide for complete burning of the material. The nitrocellulose can vary in nitrogen content, but is what is generally known as lownitrogen nitrocellulose, being combustible rather than explosive in its burning characteristics. The amount of nitrocellulose incorporated into the casing material can vary depending upon the burning characteristics desired, but is generally in the range of from 50 to weight percent. The nitrocellulose can be in the form of powder, fibers and the like.

Fibers, in staple or continuous form are used to reinforce the casing and improve its dimensional stability. The fibers, of course, must be combustible at the ignition temperature and can be of synthetic or natural origin. Acrylics, such as acrylonitrile; polyolefins, such as polypropylene; polyamides and polyesters are all exemplary of synthetic fibers which can be used. The faster burning natural fibers, such as cotton, hemp, jute, kraft fibers or other cellulosic materials are preferred. The amount of fiber depends upon the casing strength desired and usually is in the range of 10-25 weight percent.

A resinous component, such as polyvinyl formal, polyvinylacetate, polyacetal, polymethylmethacrylate or acrylonitrile, is employed as a binder for the nitrocellulosefiber mixture. The amount of binder will vary depending upon the manufacturing technique and the desired strength characteristic, but will generally be in the range of 10-25 weight percent. If desired, additives such as burn promoting agents and crystalline explosives can be incorporated into the casing material. Diphenylamine, cyclotetramethylene tetranitramine and diaminotrinitrobenzene are burn promoting additives which can be used.

The nitrocellulose-fiber-resin mixture can be formed into a casing 12 by many conventional methods such as compression molding, felting, injection molding and the like. If molded as separate elements, the tubular casing 16 and base 17 should be joined and sealed in such a manner as to prevent penetration of water or oil into the casing 12.

The above-described combustible cartridge is improved and rendered practical for use under a variety of field conditions by first incorporating a water repellent organosilicon compound in the casing material and then applying a substantially continuous coating to at least the exterior casing surface, the coating being a room temperature curing organosiloxane resin. The resin coating acts as a primary barrier to moisture, in the form of liquid or vapor, and oil. The water repellent organosilicon, which is incorporated into the porous casing, serves to prevent wicking or transmission of liquid water throughout the casing in the event that the surface coating is damaged but does not destroy the porosity of the material.

The water repellent organosilicon compounds (a) used in the practice of the invention include alkali metal siliconate salts for example any lithium, sodium, potassium or cesium salt of the monomethyl siliconate, monoethyl siliconate, monopropyl siliconate, monovinyl siliconate, or monoallyl siliconate. These salts can contain an average from less than one to three inclusive alkali metal atoms per silicon atom. Preferably, the salts contain an average of from one to two alkali metal atoms per silicon atom. If desired, two or more salts can be employed. The sodium salts are preferred, in particular the sodium salt of monomethyl siliconate which contains about one sodium atom per silicon atom. These alkali metal siliconates are well known in the art, being described in Canada Pat. No. 736,544.

Also suitable for use as water repellents are silanes of the formula R,,SiX., and the water soluble partial hydrolyzates thereof wherein n is an integer having a value of from 1 to 3. As described above R can be any monovalent hydrocarbon radical of from 1 to 30 inclusive carbon atoms, such as alkyl radicals such as methyl, ethyl, isopropyl, hexyl, octadecyl or myricyl; alkenyl radicals such as vinyl, allyl, hexenyl; alkynyl radicals such as propargyl; cycloaliphatic radicals such as cyclopentyl, cyclohexyl or cyclohexenyl; aromatic hydrocarbon radicals such as phenyl, tolyl, xylyl, xenyl, naphthyl or anthracyl and aralkyl hydrocarbon radicals such as benzyl, beta-phenylethyl, beta-phenylpropyl or gamma-tolylpropyl.

X can be any hydrolyzable group such as halogen atoms such as F, Cl, Br or 1; groups of the formula OZ when 2 is any hydrocarbon or halogenated hydrocarbon group such as methyl, ethyl, isopropyl, octadecyl, allyl, hexenyl, cyclohexyl, phenyl, benzyl, beta-phenylethyl, 2-ch1oroethyl, chlorophenyl, 3,3,3-trifluoropropyl or bromocyclohexyl; any hydrocarbon ether radical such as Z-methoxyethyl, 2-ethoxyisopropyl, 2-butoxyisobutyl, p-methoxyphenyl or (CH CH O) CH any acyl radical such as acetyl, propionyl, benzoyl, cyclohexoyl, acrylyl, methacrylyl, stearyl, naphthoyl, trifiuoroacetyl, chlorobenzoyl or bromopropionyl; or any N,N-amino radical such as dimethylamino, diethylamino, ethylmethylamino, diphenylamino, or dicyclohexylamino. X can also be any amino radical such as Nl-l dimethylamino, diethylamino, methylphenylamino or dicyclohexylamino; any ketoxime radical of the formula -ON=CM or -ON=CM in which M is any monovalent hydrocarbon or halogenated hydrocarbon radical such as those shown for 2 above and M is any divalent hydrocarbon radical both valences of which are attached to the carbon, such as hexylene, pentylene or octylene; ureido groups of the formula N(M)CONM in which M is defined above and M" is H or any of the M radicals; carbamate groups of the formula --OOCNMM" in which M and M" are defined above, or carboxylic amide radicals of the formula NMC=O(M") in which M and M are defined above. X can also be the sulfate group or sulfate ester groups of the formula OSO OM) where M is defined above; the cyano group; the isocyanate group; and the phosphate group or phosphate ester groups of the formula --OPO(OM) in which M is defined above. The term hydrolyzable group means any group attached to the silicon which is hydrolyzed by water at room temperature to form 5 SiOH.

Especially preferred are silanes of the fonnula R' -,SiOR' and R',Si(OR) and in which each R is independently selected from the group consisting of a lower alkyl of from one to three carbon atoms. A relatively inexpensive source of the water repellent silanes are the chlorosilicon compounds produced as by-products in the direct process method for preparing alkyl silicon chlorides by the reaction of alkyl chlorides with silicon. A mixture of by-product chlorosilicon compounds contained in the residue from this direct process can by hydrolyzed to provide water soluble hydrolyzate which is neutralized by the addition of calcium hydroxide. The above described water repellents can be incorporated into the casing material by a variety of methods, such as by impregnating, for example dipping or spraying; mixing the organosilicons into a pulp mixture which is then molded or felted to form the casing or by pretreating the reinforcing fiber component of the mixture with the defined organosilicon compounds. Also, the water repellents can be incorporated into the casing material by exposing the molded casing to the organosilicon compound which is entrained in steam. When the water repellent organosilicon compounds are incorporated in the form of an aqueous dispersion, the casing must be dried to remove free water.

The amount of organosilicon compound which is incorporated is sufficient to render the casing substantially impermeable or nontransmittive of liquid water. This amount will vary with the density and porosity of the casing material, but is generally in the range of 0.1 to 3 percent by weight of the casing material. By substantially impermeable to liquid water" it is meant that the casing material, after incorporation of the water repellent, does not transmit liquid water through a 100 mil thickness after having sustained the efi'ects of a 12- inch head of water for 1 hour.

The defined water repellent organosilicon compounds are very poor film formers, thus the porosity of the casing is lowered by only a small amount, for example by 20 percent of its untreated value. The retention of the substantial amount of porosity throughout the casing material is necessary to flame propagation and complete combustion of the casing during firmg.

The continuous coating of organosiloxane resin on the exterior surface of the casing serves as the primary barrier to penetration by oil and moisture. Silicones in general are considered poor candidates in material applications where combustibility is a necessary characteristic and the above described organosiloxane resin cannot be considered combustible. However, the resin is tailored, by means of controlling the degree and type of substitution on the silicon atom, to provide a flexible film which will not crack during normal handling, yet had sufiicient rigidity to shatter upon firing. This flexible frangible film is shattered into fine particles and carried away by the hot combustion gases during firing of the cartridge, thus eliminating a major source of residue in the breech of the gun.

In order to obtain the desired combination of properties, a major portion, mol percent, of the organo substituents in the siloxane resin must be either lower alkyl of one to six carbon atoms or phenyl radicals. Thus the siloxy units of the resin include Cfl SiO C H SiO C H (Cl-l )SiO, (C H SiO, (Cl-1 SiO units, C H-,(C H )Si0 and C H SiO It is preferred that at least 50 percent of the substituents be phenyl radicals. Those resins have a degree of substitution of less than 1.2 are brittle and easily cracked during handling. The resin having a degree of substitution of greater than 1.8 have elastomeric properties, thus are not frangible, and leave a great amount of residue after firing. Because of these limitations the resin is a combination of the monoorganosiloxy units and diorganosiloxy units described above with the preferred resins having a degree of substitution of from 1.3 to 1.6

Since the nitrocellulose casing cannot be exposed to high temperatures for any long period of time, the organosilicon resin must be one that cures at room temperature to form the flexible frangible coating. The described resins cure at room temperature as a result of the remaining functionality, for example acetoxy or methoxy substituents which condense upon exposure to atmospheric moisture. The resins are generally prepared by hydrolysis of the corresponding chlorosilanes. The hydrolyzate contains uncondensed hydroxyl groups which can then be reacted with functional silanes, such as trimethoxychlorosilane or triacetoxysilanes, to obtain the room temperature curing properties. The room temperature curing properties of materials containing functionality, such as acetoxy functional resins, are well known and illustrated in US. Pat. Nos. 2,934,519 and 3,032,529. If desired, condensation catalysts, such as dibutyltin dilaurate, can be used to accelerate the curing at room temperature.

One preferred resin for use in the invention is a ketoxime functional organosiloxane block copolymer consisting essentially of (a) 5 to 25 inclusive mol percent of diorganosiloxane units wherein the diorganosiloxane units are bonded through silicon-oxygen-silicon bonds forming a polydiorganosiloxane block having an average from 6 to 15 inclusive diorganosiloxane units per block, the polydiorganosiloxane being at least mol percent dimethylsiloxane or phenylmethylsiloxane units, any remaining units being selected from the group consisting of phenylmethylsiloxane and monomethylsiloxane units (b) 50 to 75 inclusive mol percent organosiloxane units having an average formula R,SiO wherein at has a value of from 1 to 1.3 inclusive and R" is an organic group selected from the group consisting of phenyl radicals, methyl radicals, ethyl radicals and propyl radicals, at least 50 mol percent of these organic groups being phenyl radicals, the organosiloxane units comprising a block of at least 3 siloxane units, the siloxane units being selected from the group consisting of monoorganosiloxy and diorganosiloxy units; and (c) 3 to 20 inclusive mol percent of endblocking ketoxime siloxane units of the formula RSi(O-N=X),,O;, where y has an average value of from 1.8 to 2 inclusive, R' is an organic radical selected from the group of alkyl radicals having one to five inclusive carbon atoms, phenyl radicals and vinyl radicals and X is selected from the group consisting of radicals of the formula O and Q'C= in which each Q is a radical independently selected from the group consisting of monovalent hydrocarbon radicals and monovalent halogenated hydrocarbon radicals; and Q is a divalent hydrocarbon radical; the mol percentages of (a), (b) and (c) being based on the total number of siloxane units in the organosiloxane block copolymer.

This room temperature curable composition can be prepared by several methods. The best method is to couple a hydroxyl-terminated polydiorganosiloxane with an aromaticcontaining organosiloxane resin having hydroxyl groups by reaction with a trifunctional organosilane. The resulting block copolymer is itself hydroxylated and then reacted with monoorganotriketoximesilane to yield the described composition. Alternatively, the hydroxylated terminated polydiorganosiloxane can be cohydrolyzed with a trifunctional organosilane in the proper proportion. Examples of Q and Q can be found in US. Pat. Nos. 3,184,427 and 3,189,576.

The resin is applied from a solution to the surface of the casing 12 by any conventional means such as spraying, dipping or brushing. Of course, when the entire casing is dipped into a solution of the resin the inner surface of the casing is also coated. Any suitable solvent which does not react with functional groups of the resin and which have no adverse effect on the casing material can be employed to form the coating solution. Such solvents include benzene, toluene, xylene, perchloroethylene, mineral spirits and chlorobenzene. If desired, thixotropic agents such as silica can be added to the solution to provide for a uniform coating. Care should be taken during the coating operation to avoid pin holes in the thin film. The amount of resin coated onto the shell casing will vary but is generally in the range of from 2 to 15 weight percent, thus providing 1 to 5 mil thickness of coating.

It is also desirable that a heat conductive substance, such as carbon black, silicon carbide, or powdered metal, for example aluminum, be incorporated in the resin coating. These materials serve to transfer the heat of a point of combustion, such as a small piece of burning char or cigarette, over a large area thus minimizing fire hazards from such materials.

In its broadest aspect, the invention contemplates, as an ar ticle of manufacture, combustible fiber-reinforced nitrocellulose products having incorporated therein a water repellent organosilicon compound as previously defined in an amount sufi'rcient to render the material substantially impermeable to liquid water and having a continuous coating on the surface thereof of the described room temperature curable organosiloxane resin. Thus, mats of fiber-reinforced nitrocellulose, caseless ammunition in which the propellent charge itself forms the cartridge casing and other types of combustible containers can be manufactured in accordance with the present invention.

In FIG. 2, fiber-reinforced nitrocellulose prepared in accordance with the invention is illustrated. The water repellent organosilicon compound 19 is incorporated throughout the casing material 12, while the organosiloxane resin 20 forms a continuous coating on the exterior surface.

The following example is illustrative, but not to be construed as limiting, of the invention which is properly delineated in the claims.

EXAMPLE Combustible cartridges (152 mm) composed of 69 weight percent nitrocellulose, 15 weight percent kraft fibers, 15 weight percent formaldehyde resin binder and 1 weight percent of diphenylamine, were impregnated with a weight percent aqueous solution of the sodium salt of monomethyl siliconate having about one sodium atom per silicon atom. The cartridges were sprayed with the solution and allowed to dry. After drying the exterior surfaces of the cartridges were sprayed with a toluene solution of a ketoxime functional resin prepared by the reaction of monomethyldi(methylethylketoxime )siloxy terminated polydimethylsiloxane (d.p. of 14) with a hydroxylated resin having 45 mol percent CH;,SiO units, 40 mol percent c,r-r,sio,,, units, 10 mol percent (C,H,),Si0,,, units and 5 mol percent CH;,(C,,l-l,)SiO units and methyltri(methylethylketoxime)silane. The coating of monomethyldi(methylethylketoxime)siloxy terminated organosiloxane block copolymer was allowed to cure at room temperature in the presence of atmospheric moisture. Curing was complete after 1 hour to form a non-tacky coating on the surface.

The cartridges were loaded with propellant primed and fitted with a projectile. A portion of the assembled cartridges were exposed to a simulated rain stonn for 12 hours. The cartridges, both dry and wet, were fired from a 155 mm howitzer. Muzzle velocities were comparable to those of untreated cartridges. The dry cartridges left no residue in the breech after firing. The cartridges which had been exposed to the rain left little or no residue in the breech, the largest fragment residue totaling only 3-4 square inches. Untreated cartridges fabricated from the same components leave a considerable amount of residue in the breech which must be removed prior to firing another round.

That which is claimed is:

1. An article of manufacture having a surface of porous fiber-reinforced nitrocellulose, the fiber-reinforced nitrocellulose having incorporated therein a water-repellent organosilicon compound in an amount sufficient to render the nitrocellulose substantially impermeable to v liquid water, the or ganosilicon compound being selected from the group consisting of alkali metal salts of monoorganosilconates in which the organic group is a lower alkyl of from one to three inclusive carbon atoms and silanes of the formula R,,SiX., and watersoluble hydrolyzates thereof in which R is a monovalent hydrocarbon radical of from 1 to 30 inclusive carbon atoms, X is a hydrolyzable group and n is an integer having a value of l or 3; said surface having a continuous coating thereon of a room temperature curable organosiloxane resin, said organosiloxane resin having an average of from 1.2 to 1.8 organic groups per silicon atom, at least mol percent of the organic groups being selected from the group consisting of lower alkyl and phenyl radicals, any remaining organic groups being selected from the group consisting of alkoxy radicals having from one to four inclusive carbon atoms, acyloxy radicals of no more than eight carbon atoms and ketoxime radicals.

2. The article of claim 1 wherein the nitrocellulose has incorporated therein an alkali metal salt of a monoorganosiliconate in which the organic group is a lower alkyl radical of from one to three inclusive carbon atoms.

3. The article of claim 2 wherein the nitrocellulose has incorporated therein monomethyl sodium siliconate.

4. The article of claim 2 wherein the siloxane resin contains from 3 to 20 mol percent of ketoxime siloxy units.

5. An article in accordance with claim 4 wherein the organosiloxane resin consists essentially of a. 5 to 25 inclusive mol percent of diorganosiloxane units wherein the diorganosiloxane units are bonded through silicon-oxygen-silicon linkages to form a diorganosiloxane block having an average of from 6 to 15 inclusive siloxy units per block, the polydiorganosiloxane being at least mol percent dimethylsiloxane' or phenylmethylsiloxane units any remaining units being selected from the group consisting of phenylmethylsiloxane and monomethylsiloxane units;

. 50 to 75 inclusive mol percent organosiloxane units of the general formula R" ,.SiO wherein x has a value of from 1 to 1.3 inclusive and R" is selected from the group consisting of methyl, ethyl, propyl and phenyl radicals, at least 50 mol percent of the R" substituents being phenyl radicals, the organosiloxane units comprising a block of at least 3 siloxane units, the siloxane units being selected metal salt of a monoorganosiliconate in which the organic group is a lower alkyl of one to three inclusive carbon atoms.

10. A cartridge in accordance with claim 9 wherein the organosilicon compound is monomethyl sodium siliconate.

halogenated hydrocarbon radicals and Q is a divalent hydrocarbon radical; the mol percentages of (a), (b) and being based on the total number of siloxane units present.

6. An article in accordance with claim wherein the resin is terminated with monomethyldi(methylethylketoxime)siloxy units.

7. In a combustible cartridge having a porous casing composed of fiber-reinforced nitrocellulose which forms an exteri or cartridge surface; the improvement consisting essentially of:

a. a water repellent organosilicon compound incorporated into said casing in an amount sufficient to render said casing substantially impermeable to liquid water, said organosilicon compound being selected from the group consisting of alkali metal salts of a monoorganosiliconate in which the organic group is a lower alkyl radical of from one to three inclusive carbon atoms, and silanes of the formula R,,SiX.,-,, and water-soluble hydrolyzates thereof, in which R is a monovalent hydrocarbon radical of from 1 to 30 carbon atoms, X is a hydrolyzable group and n is an integer having a value of l to 3 inclusive; and

b. a continuous coating on the exterior casing surface of a room temperature curable organosiloxane resin having an average of from 1.2 to 1.8 organic groups per silicon atom, at least 80 mol percent of said organic groups being selected from the group consisting of lower alkyl radicals and the phenyl radical, any remaining organic groups being selected from the group consisting of alkoxy radicals of from one to four carbon atoms, acyloxy radicals of no more than eight carbon atoms and ketoxime radicals.

8. A cartridge in accordance with claim 7 wherein the coating (b) is cured.

9. A cartridge in accordance with claim 7 wherein the or- 11. A cartridge in accordance with claim 9 wherein the organosiloxane resin contains ketoxime radicals.

12. A cartridge in accordance with claim 11 wherein the organosiloxane resin consists essentially of a. 5 to 25 inclusive mol percent of diorganosiloxane units wherein the diorganosiloxane units are bonded through silicon-oxygen-silicon linkages to form a diorganosilox ane block having an average of from 6 to 15 inclusive siloxy units per block, the polydiorganosiloxane being at least mol percent dimethylsiloxane or phenylmethylsiloxane units any remaining units being selected from the group consisting of phenylmethylsiloxane and monomethylsiloxane units;

b. 50 to 75 inclusive mol percent organosiloxane units of the general formula R",SiO wherein x has a value of from 1 to 1.3 inclusive and R" is selected from the group consisting of methyl, ethyl, propyl and phenyl radicals, at least 50 mol percent of the R" substituents being phenyl radicals, the organosiloxane units comprising a block of at least 3 siloxane units, the siloxane units being selected from the group consisting of monoorganoand diorganosilox y units; and

c. to 20 inclusive mol percent of endblocking ketoxime siloxane units of the formula R'Si(O-N=X),,O in which y has a value of from 1.8 to 2 inclusive, R is an organic radical selected from the group consisting of alkyl radicals having from one to five inclusive carbon atoms, phenyl radicals and vinyl radicals and X is selected from the group consisting of Q and Q'C= in which each Q radical is independently selected from the group consisting of monovalent hydrocarbon radicals and monovalent halogenated hydrocarbon radicals and Q is a divalent hydrocarbon radical; the mol percentages of (a), (b) and (0) being based on the total number of siloxane units present,

13. A cartridge in accordance with claim 12 wherein the resin is terminated with monomethyldi( methylethylketoxime )siloxy units. 

2. The article of claim 1 wherein the nitrocellulose has incorporated therein an alkali metal salt of a monoorganosiliconate in which the organic group is a lower alkyl radical of from one to three inclusive carbon atoms.
 3. The article of claim 2 wherein the nitrocellulose has incorporated therein monomethyl sodium siliconate.
 4. The article of claim 2 wherein the siloxane resin contains from 3 to 20 mol percent of ketoxime siloxy units.
 5. An article in accordance with claim 4 wherein the organosiloxane resin consists essentially of a. 5 to 25 inclusive mol percent of diorganosiloxane units wherein the diorganosiloxane units are bonded through silicon-oxygen-silicon linkages to form a diorganosiloxane block having an average of from 6 to 15 inclusive siloxy units per block, the polydiorganosiloxane being at least 90 mol percent dimethylsiloxane or phenylmethylsiloxane units any remaining units being selected from the group consisting of phenylmethylsiloxane and monomethylsiloxane units; b. 50 to 75 inclusive mol percent organosiloxane units of the general formula R''''xSiO4 x/2 wherein x has a value of from 1 to 1.3 inclusive and R'''' is selected from the group consisting of methyl, ethyl, propyl and phenyl radicals, at least 50 mol percent of the R'''' substituents being phenyl radicals, the organosiloxane units comprising a block of at least 3 siloxane units, the siloxane units being selected from the group consisting of monoorgano-and diorganosiloxy units; and c. 3 to 20 inclusive mol percent of endblocking ketoxime siloxane units of the formula R''''''Si(O-N X'')yO3 y/2 in which y has a value of from 1.8 to 2 inclusive, R'''''' is an organic radical selected from the group consisting of alkyl Radicals having from one to five inclusive carbon atoms, phenyl radicals and vinyl radicals and X'' is selected from the group consisting of Q2 and Q''C in which each Q radical is independently selected from the group consisting of monovalent hydrocarbon radicals and monovalent halogenated hydrocarbon radicals and Q'' is a divalent hydrocarbon radical; the mol percentages of (a), (b) and (c) being based on the total number of siloxane units present.
 6. An article in accordance with claim 5 wherein the resin is terminated with monomethyldi(methylethylketoxime)siloxy units.
 7. In a combustible cartridge having a porous casing composed of fiber-reinforced nitrocellulose which forms an exterior cartridge surface; the improvement consisting essentially of: a. a water repellent organosilicon compound incorporated into said casing in an amount sufficient to render said casing substantially impermeable to liquid water, said organosilicon compound being selected from the group consisting of alkali metal salts of a monoorganosiliconate in which the organic group is a lower alkyl radical of from one to three inclusive carbon atoms, and silanes of the formula RnSiX4 n and water-soluble hydrolyzates thereof, in which R is a monovalent hydrocarbon radical of from 1 to 30 carbon atoms, X is a hydrolyzable group and n is an integer having a value of 1 to 3 inclusive; and b. a continuous coating on the exterior casing surface of a room temperature curable organosiloxane resin having an average of from 1.2 to 1.8 organic groups per silicon atom, at least 80 mol percent of said organic groups being selected from the group consisting of lower alkyl radicals and the phenyl radical, any remaining organic groups being selected from the group consisting of alkoxy radicals of from one to four carbon atoms, acyloxy radicals of no more than eight carbon atoms and ketoxime radicals.
 8. A cartridge in accordance with claim 7 wherein the coating (b) is cured.
 9. A cartridge in accordance with claim 7 wherein the organosilicon compound (a) is incorporated by means of impregnating the casing with an aqueous solution of an alkali metal salt of a monoorganosiliconate in which the organic group is a lower alkyl of one to three inclusive carbon atoms.
 10. A cartridge in accordance with claim 9 wherein the organosilicon compound is monomethyl sodium siliconate.
 11. A cartridge in accordance with claim 9 wherein the organosiloxane resin contains ketoxime radicals.
 12. A cartridge in accordance with claim 11 wherein the organosiloxane resin consists essentially of a. 5 to 25 inclusive mol percent of diorganosiloxane units wherein the diorganosiloxane units are bonded through silicon-oxygen-silicon linkages to form a diorganosiloxane block having an average of from 6 to 15 inclusive siloxy units per block, the polydiorganosiloxane being at least 90 mol percent dimethylsiloxane or phenylmethylsiloxane units any remaining units being selected from the group consisting of phenylmethylsiloxane and monomethylsiloxane units; b. 50 to 75 inclusive mol percent organosiloxane units of the general formula R''''xSiO4 x/2 wherein x has a value of from 1 to 1.3 inclusive and R'''' is selected from the group consisting of methyl, ethyl, propyl and phenyl radicals, at least 50 mol percent of the R'''' substituents being phenyl radicals, the organosiloxane units comprising a block of at least 3 siloxane units, the siloxane units being selected from the group consisting of monoorgano- and diorganosiloxy units; and c. 3 to 20 inclusive mol percent of endblocking ketoxime siloxane units of the formula R''''''Si(O-N X'')yO3 y/2 in which y has a value of from 1.8 to 2 inclusive, R'''''' is an organic radical selected from the group consisting of alkyl radicals having from one to five inclusive carbon atoms, phenyl radicals and vinyl radicals and X'' is selected from the group consisting of Q2 and Q''C in which each Q radical is independently selected from the group consisting of monovalent hydrocarbon radicals and monovalent halogenated hydrocarbon radicals and Q'' is a divalent hydrocarbon radical; the mol percentages of (a), (b) and (c) being based on the total number of siloxane units present.
 13. A cartridge in accordance with claim 12 wherein the resin is terminated with monomethyldi(methylethylketoxime)siloxy units. 